During a 21⁄2-week stretch that started when Rajon Rondo tore his anterior cruciate ligament on Jan. 25 in Atlanta, three Celtics players went down with season-ending injuries. Rondo, Jared Sullinger (back surgery) and Leandro Barbosa (knee surgery) were gone in the blink of an eye, and the losses took an enormous chunk out of the Celtics’ viability. Though the Green were 14-4 in the 18 games after Rondo’s injury, they eventually fell back to earth. When Doc Rivers lamented at the start of the playoffs that his team lacked a true point guard, the damage was obvious. So this can’t be called an underachieving season, though the Celtics’ 0-3 playoff start pointed in that direction. They also recovered with wins against New York in Games 4 and 5, letting out what perhaps was the final gasp of a great era. We might have witnessed the last hurrah for Paul Pierce and Kevin Garnett as Celtics. Both players finished with a list of injuries that could fill a sports clinic menu, further proof that health issues defined this Celtics season. The following grades are based on how each player performed based on individual expectations this season.